000 AXPZ20 KNHC 071000 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SAT NOV 07 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0815 UTC. ...TROPICAL LOWS... LOW PRES CENTERED NEAR 12N91W ESTIMATED AT 1006 MB AND IS NOW MOVING N SLOWLY IN RESPONSE TO THE UPPER TROUGH IMMEDIATELY TO ITS W WHICH IS ALSO CONTRIBUTING BOTH SOUTHWESTERLY WIND SHEAR AND DRY AIR WHICH IS BEING ENTRAINED BY THE LOW. THE SYSTEM IS EXPECTED TO DISSIPATE TO A TROUGH OVER THE NEXT 24 HOURS WITHIN THIS HOSTILE ENVIRONMENT. CURRENTLY...SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION IS DISPLACED FROM THE LOW LEVEL CENTER...BETWEEN 60 NM AND 180 NM IN THE NE QUADRANT OF THE LOW. TWO SHIP REPORTS IN THE EASTERN SEMICIRCLE OF THE LOW REPORTED WINDS IN THE 25 TO 30 KT RANGE AT 0600 UTC...BUT THESE WINDS SHOULD RAPIDLY DIMINISH TODAY AS THE LOW WEAKENS. LOW PRES CENTERED NEAR 12N116W IS ESTIMATED AT 1010 MB. THE SURFACE LOW IS UNDER AN UPPER ANTICYCLONE...AND THE ASSOCIATED UPPER DIFFLUENCE HAS BEEN ENHANCING CONVECTION. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION LIES WITHIN 180 NM NW AND SE QUADRANTS OF THE LOW. THIS LOW IS EXPECTED TO WEAKEN OVER THE NEXT 24-36 HOURS AS THE UPPER JET TO ITS N SINKS SOUTHWARD...PROVIDING 30 TO 40 KT OF SHEAR OVER THE SYSTEM. ...ITCZ... THE ITCZ AXIS EXTENDS ALONG 07N77W TO 11N87W TO 07N97W TO 12N115W TO 08N140W. SCATTERED MODERATE CONVECTION CAN BE FOUND NEAR PANAMA WITHIN 60 NM N AND 120 NM S OF THE ITCZ AXIS BETWEEN 78W AND 82W. SCATTERED MODERATE TO STRONG CONVECTION LIES WITHIN 90 NM S OF THE ITCZ AXIS BETWEEN 98W AND 101W. ...DISCUSSION... N OF 20N... AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 08N113W WITH A RIDGE AXIS EXTENDING NE TO MANZANILLO...MEXICO AND CONTINUING N INTO TEXAS. AN UPPER LOW LIES OVER THE NORTHERN GULF OF CALIFORNIA NEAR 29N113W AND IS APPROACHING THIS RIDGE AXIS FROM THE W. THE TROPICAL MOISTURE PLUME THAT EXTENDED FROM THE ITCZ REGION TO THE EASTERN EDGE OF THIS UPPER LOW THIS TIME YESTERDAY HAS BEEN CUT OFF. ONLY HIGH CLOUDS REMAIN...PRIMARILY OVER THE NORTHERN HALF OF THE GULF OF CALIFORNIA AS WELL AS OVER NW MAINLAND MEXICO. THIS UPPER LOW WILL CONTINUE E AWAY FROM THE FORECAST AREA OVER THE NEXT FEW DAYS. THERE IS LITTLE INDICATION OF THE UPPER LOW AT THE SURFACE WHERE A HIGH PRES RIDGE STEMMING FROM A 1032 MB HIGH NEAR 36N152W DOMINATES THE REMAINDER OF NORTH WATERS. THE PRES GRADIENT BETWEEN THIS HIGH AND LOW PRES OVER THE GULF OF CALIFORNIA HAS BROUGHT 20 KT NORTHERLY WINDS OFF THE W COAST OF BAJA CALIFORNIA. THESE WINDS SHOULD DISSIPATE OVER THE NEXT FEW HOURS AS A COLD FRONT BEARS DOWN ON THE HIGH PRES SYSTEM FROM THE NW AND WEAKENS THE RIDGING. WHILE THIS FRONT IS EXPECTED TO DISSIPATE BEFORE IT CAN REACH FORECAST WATERS...LONG PERIOD NW SWELL FROM THE SYSTEM IS ALREADY BEGINNING TO PUSH INTO NW WATERS WITH SIGNIFICANT WAVE HEIGHTS INCREASING TO 18 FT OVER NW WATER THIS MORNING. HIGHEST SEAS WILL SHIFT E QUICKLY TODAY ACROSS N WATERS...WITH THE LEADING EDGE OF THE SWELL TRAIN PROGRESSING SE. S OF 20N... ASIDE FROM THE LOW PRES SYSTEMS DESCRIBED ABOVE AND THE GAP WINDS DESCRIBED BELOW...EASTERLY TRADE WINDS ARE THE DOMINANT FEATURE OF NOTE. 20 TO 25 KT TRADES ARE CURRENTLY LIMITED TO BETWEEN 10N AND 20N W OF 127W...WITH A SMALL AREA OF 20 TO 25 KT WINDS ASSOCIATED WITH THE LOW PRES SYSTEM NEAR 12N116W. THE AREA OF STRONGEST TRADE WINDS WILL SHIFT S IN RESPONSE TO THE AFOREMENTIONED REORGANIZATION OF THE HIGH PRES SYSTEM TO THE NORTH. ANOTHER WEAK LOW PRES SYSTEM LIES NEAR 10N108W. ACCORDING TO THE 0504 ASCAT PASS...THE LOW HAS A SMALL AREA OF 20 TO 25 KT WINDS WITHIN 90 NM IN ITS N QUADRANT. SCATTERED MODERATE CONVECTION CAN CURRENTLY BE FOUND WITHIN 90 NM NW AND 60 NM SE SEMICIRCLES OF THE LOW WHICH NOW LIES UNDER THE ANTICYCLONE IN A FAVORABLE AREA FOR CONVECTION. CONDITIONS SHOULD BECOME MORE HOSTILE FOR THE SYSTEM OVER THE NEXT DAY OR TWO...AND THIS LOW IS EXPECTED TO DISSIPATE WITH LITTLE FANFARE. GAP WINDS... A PARTIAL ASCAT PASS FROM 0324 UTC SHOWED WINDS IN THE 30 TO 33 KT RANGE IN THE GULF OF TEHUANTEPEC. CONSIDERING THE PASS OMITTED A PORTION OF THE AREA BELIEVED TO HAVE THE STRONGEST WINDS AND THE FACT THAT ASCAT GENERALLY RUNS LOW WITH WINDS NEAR GALE FORCE AND HIGHER...THERE IS LIKELY STILL A GALE HERE THAT WILL CONTINUE THROUGH THE MORNING HOURS. HOWEVER...THERE IS A CONSIDERABLE AMOUNT OF UNCERTAINTY WITH THE FORECAST FOR THE STRENGTH AND POSITION OF LOW PRES IN THE BAY OF CAMPECHE...THE PERSISTENT LOW PRES NEAR 12N91W THAT IS NOW DRIFTING N...AND TROPICAL STORM IDA NOW OVER THE EASTERN GULF OF HONDURAS AND FORECAST TO MOVE NORTHWARD AND STRENGTHEN. ALL OF THESE FACTORS WILL INFLUENCE THE WIND...OR LACK OF WIND...IN THE GULF OF TEHUANTEPEC OVER THE NEXT FEW DAYS. DEPENDING ON THE ORIENTATION OF THE LOW PRES CENTERS N OF THE AREA...ANOTHER N SURGE MAY OCCUR AS EARLY AS SUN IN THE GULF OF TEHUANTEPEC. $$ SCHAUER